There are some applications for which side unloading dump vehicles are either desirable or essential. By way of example, it is not unusual for two trailers to be pulled one behind the other in what is known as a "Super B" trailer combination. In view of the proximity of the second trailer, the only manner in which the first trailer can dump is off to the side. By further way of example, in the construction industry problems are frequently incurred in dumping loads required for road widening. There is generally difficult or impossible due to space constraints for a rear unloading vehicle to positioned itself transversely across the roadway to dump in the desired location. A side unloading dump vehicle can take a number of forms; such as a dump truck, a trailer, or a rail car.
There are a number of side unloading dump vehicles that are disclosed in the patent literature, such as U.S. Pat. No. 5,480,214 which issued to Rogers in 1996 and U.S. Pat. No. 5,597,211 which issued to Golden in 1997. There patents both disclose side dumping mechanisms that tip a containment tub to one side in order to allow material to dump out of a top of the containment tub. This mechanism works in a satisfactory manner only so long as the material in the containment tub does not stick. Should the material stick with the containment tub in an angled and over centered dumping position, there is a danger that the vehicle will become top heavy and tip over.